1. Field of the Invention
This invention relates to a carrier for supporting orthodontic appliances such as brackets and buccal tubes of the type used in orthodontic treatment. The carrier is particularly useful for supporting the appliances during their manufacture, during the time that the appliances are received within a container for shipment to an end user and also during the time that the brackets are arranged in a set-up tray in a dental operatory in preparation for application to a patient's tooth surface.
2. Description of the Related Art
Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct positions. Tiny orthodontic appliances known as brackets are connected to exterior surfaces of the patient's teeth, and an archwire is placed in a slot of each bracket. The archwire forms a track to guide movement of the teeth to desired positions for correct occlusion. End sections of the archwire are often received in appliances known as buccal tubes that are fixed to the patient's molar teeth.
In the past, orthodontic appliances were connected to teeth by welding or brazing each bracket or buccal tube to a band that was then placed over the desired tooth in encircling relation. In more recent years, however, it has become common practice to bond orthodontic appliances directly to the surface of the tooth. Orthodontic brackets that are directly bonded to tooth surfaces provide a more aesthetic appearance than the appearance of brackets that are welded to bands, and help alleviate the problem of a "tinsel tooth" or "metallic mouth" appearance that is often associated with orthodontic treatment.
For many years, it was common practice to apply orthodontic adhesive to the base of directly-bonded appliances immediately before the appliances were placed on the tooth. In some instances, a quantity of adhesive was dispensed onto a mixing pad or dispensing well and a small spatula or other hand instrument was then used to apply a small dab of adhesive to each appliance. In other instances, a quantity of adhesive was dispensed from a syringe directly onto the base of the appliance.
Adhesive precoated brackets are also now available and represent a significant advantage to the orthodontist. Adhesive precoated brackets have a bonding base upon which the manufacturer has applied a precise quantity of adhesive such as a photocurable adhesive. When it is desired to mount the bracket on a tooth, the bracket is simply removed from the package and is placed directly onto the tooth surface.
Examples of adhesive precoated brackets are described in U.S. Pat. Nos. 4,978,007, 5,015,180 and 5,328,363, all of which are assigned to the assignee of the present invention. In certain embodiments of the inventions described in those patents, the bracket and adhesive are packaged in a container that protects the adhesive from light, evaporation, oxidation, contamination, humidity and sublimation. In some of those embodiments, the coating of adhesive on the packaged bracket is in contact with a release liner or coating that helps prevent the adhesive from being disturbed when the bracket is lifted from the package for use.
As can be appreciated, adhesive precoated brackets represent a significant time savings for the orthodontic practitioner because the adhesive need not be carefully applied to the base of each bracket before placement of the bracket onto the patient's tooth. In addition, the manufacturer can control the quantity of adhesive placed on the bracket so that there is sufficient adhesive to substantially fill the space between the bracket base and the tooth when the bracket is pushed into position, and yet there is not an inordinate amount of adhesive that might otherwise require excessive clean-up around the perimeter of the bracket base. Optionally, the adhesive is a light-curable adhesive so that the bracket can be carefully positioned in a proper orientation on the tooth surface before a curing lamp is activated to cure the adhesive and securely fix the bracket in place.
In general, the adhesives used for adhesive precoated brackets that are contained in a package having a release liner or coating are more viscous (i.e. less fluid) than other available orthodontic bonding adhesives, in part to ensure that the adhesive retains its shape and does not separate or distort when the bracket is lifted from the package for use. However, some orthodontists prefer the use of less viscous (i.e. more fluid) adhesives in order to facilitate manipulation of the bracket before the adhesive is cured. For example, brackets with less viscous adhesives are relatively easy to slide along the tooth surface when an effort is made align the bracket in a proper, precise orientation on the tooth before the adhesive is cured.
Some practitioners prefer two component chemical-cure adhesives (such as Unite brand adhesive, from 3M Unitek Corporation) to light-curable adhesives. It has been proposed in the past to package orthodontic brackets with one component of a chemical-cure adhesive on each bracket base, and then apply the second component to each bracket base and/or to the patient's tooth once the bracket is removed from the package. Presently, there is a need in the art for an improved package suitable for both chemical-cure adhesives as well as light-curable adhesives.
Moreover, there is increased interest in optimizing the manufacture of orthodontic brackets. Manufacturing optimization may include, for example, automation of the processes for handling of the brackets from the time of manufacture to the time of packaging, as well as increased efficiency of applying the adhesive to the base of the brackets in instances where the brackets are sold with a coating of adhesive. Such improvements in manufacturing can not only reduce costs and processing time, but also may result in a decrease of problems that might otherwise attributed to human error.